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Old 13th February 2014, 06:11 AM   #4991
SSerg is offline SSerg  Russian Federation
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Quote:
Originally Posted by Rick Miller View Post
Anyone have any thoughts on this?
I would not call a shunt regulator current source. This is confusing.

For supply voltage -15 V can be used as a shunt regulator and serial stabilizer.
Personally, I prefer a shunt regulator. He has a constant current consumption.
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Old 13th February 2014, 06:19 AM   #4992
galeb is offline galeb  Spain
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Hi Rick,

Yes, -15vdc is not only important, but hypercritical. I've used a lot of kind of regulators. Finally the one I'm using is this:

A separate power transformer, hyperfast diodes, a discrete regulator, 4x22.000uf/25v capacitors and closest as possible to the -15vdc pin, a 1uf capacitor from Illinois capacitor, the smd 1210 size ones for high frequency.

The regulator has to be kept as simple as possible, using only one active element to regulate the voltage, do not use op amps for error amplifier. I have been using a lot of transistors, finally the BD244C and BD243C for the positive has been chosen. These ones have the best HF response.

Of course for the +5&-5 you must use the same principle, but, if you want, you can use instead of 2x22.000uf/25v, only 2 units........

Kindest regards, and I hope this helps a little.
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Old 13th February 2014, 02:44 PM   #4993
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Quote:
Originally Posted by Rick Miller View Post
Back to the power supply, I believe the -15v supply is the most important for the best sound. It feeds current sources in the 1541. As far as the regulator for this -15v, I was told that a current source should not feed a current source (1541). It is better to have a voltage source (series reg) feed a current source (1541). Not a shunt reg (current source) feeding the current sources in the 1541 (-15v).

Anyone have any thoughts on this?
These two "current sources" are different beasts, as far as I see, the internal one tries not to maintain a stable voltage like the first one.
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Old 13th February 2014, 04:51 PM   #4994
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Thanks for all the replies, I have found that the -15v supply to the 1541 has more affect on the sound than any on the other supplies. That is why I am trying to make it as good as possible. I see Galeb has also found out how important the -15v supply is to good sound.

I wonder how many people are using series regs and how many are using shunt regs? I am using a series right now.
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Old 13th February 2014, 06:33 PM   #4995
Eldam is offline Eldam  France
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Hi Rick,

You damned right,

How the -15V are important is a known fact since the first tweaks in the end of the 80s'.

Look for old e-papers on the web learn you a lot too about it. ECDesigns explain a lot how the ground design and routing are important too like others :T Loesch and some famous diyers also.

I would like to have a benchmark of the most efficient and simple ones. A very stable - 15 v with a triple Pi filter (coil no resistor) can be a beginning... I'm curious to know the results of the smd low noise reg. ?!

Tell us if you find interesting results
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Old 13th February 2014, 11:01 PM   #4996
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Hi Eldam, thanks for the information. Lets see if ECDesigns reads this and tells us about the -15v reg and supply that gave him the best results, after all this is his great thread.
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Old 15th February 2014, 12:46 PM   #4997
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Quote:
Lets see if ECDesigns reads this and tells us about the -15v reg and supply that gave him the best results
I still follow the thread when I have time.


Anyway, the last TDA1541A module I tested had local, discrete shunt regulators driven by external capacitance multiplier & current limiting circuit.

In the new projects like the SD1-player and the UD1-streamer (attached picture shows early prototype) I use “quatrode” series regulators exclusively. These consist of a filtered ultra low noise precision voltage reference that drives a unity gain super buffer. These voltage regulators are more efficient compared to shunt regulators and allow the use of small mains transformers with very low stray capacitance.

TDA1541A -15V is most sensitive to power supply ripple (check datasheets) and it powers sensitive on-chip analogue circuits. So clean -15V power supply is advisable.
Attached Images
File Type: jpg ud1-2.jpg (95.7 KB, 961 views)
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Old 15th February 2014, 10:05 PM   #4998
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Thanks eddesigns, I always look forward to you posts. Any chance you could explain you "quatrode" regulator in more detail? It sound like just the thing for the -15v supply. Your streamer looks very good.
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Old 15th April 2014, 08:34 AM   #4999
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Hi Rick Miller,

Sorry for the late reply, too much to do, too little time.

Quote:
Any chance you could explain you "quatrode" regulator in more detail? It sound like just the thing for the -15v supply.
The quatrode regulator basically consists of a reference voltage and a buffer circuit. I use a LM329 (approx. 7V). It’s output voltage (and its noise) are attenuated by a resistive divider. The resistive divider output is filtered in order to get a clean reference voltage. In the SD1-player I need multiple output voltages (4 in total) that are all derived from a single LM329.

The quatrode circuit consists of MOSFETs and Darlingtons, it is an universal building block with 4 connections, in, out, minus, and plus. It has very high input impedance, very low output impedance, large bandwidth, low noise, excellent step response and line / load regulation.

It is also possible to use the quatrode circuit as shunt regulator. For the quatrode shunt regulator the reference voltage equals Vout - 0.6V, for quatrode series regulator the reference voltage equals Vout +0.6V.

Quatrode series regulators are useful when load current changes significantly, digital circuit (processor) for example. Shunt regs have a specific bias current so peak current is limited by it, these shunt regs are suitable for powering loads with (almost) constant load current.

I use 3 quatrode shunt regulators in the new TDA1541A project (The TDA1541A DAC project has been finally picked up again).


Quote:
Your streamer looks very good.
“small and nice” as we call it over in Holland. This USB DAC prototype is only 12 millimeters high and fits in the palm of your hand. It is based on SD1-player circuits like local, discrete masterclock, slaved source (asynchonous USB), quatrode regulators and so on.
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Old 18th April 2014, 08:59 AM   #5000
Sven257 is offline Sven257  United States
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Hi John, (EC Designs)

I'm happy to see that you have picked up the TDA1541 DAC project again...
Does that mean you have some new ideas/solutions to deal with the pesky 'DEM circuit'??

Peter
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